This invention relates to a windscreen wiper blade arrangement.
While the specification refers throughout to "cars", it is to be understood that this term is intended to include all vehicles using handed driving arrangements and therefore includes, amongst others, vans, lorries, buses and coaches.
With the advent of specialised windscreen wiper blades dedicated to provide an adequate wipe in conditions in which wind lift of the blades can occur, it has been found necessary to design windscreen wiper blades which are asymmetrical about their longitudinal axis. With these types of blade, orientation is of the essence since, to reduce the effect of wind lift, it is essential for a particular side of the blade to effectively face into the air ("wind") moving over the car. Should the wrong side of the blade face into the wind, not only is the advantage of the specially shaped blades lost but the ability of the wind to lift the blade from the surface of the windscreen can actually be increased.
Common wiping of the windscreen using a dual blade wiper system provides a pattern of wipe in which the blade moves in an arc from an upright position towards the offside of a vehicle to a horizontal position towards the near side of the vehicle. With this pattern of wipe, it will be clear that the pattern for left-hand drive cars and right-hand drive cars will be exactly opposite.
Tests involving a study of the wind lift characteristics of modern wiper blades has shown that, in general, the air flow is such that the special blades only need to be fitted to the driver's side, the passenger side working adequately with standard blades, but of course, special blades may be fitted to both driver's and passenger's side for aesthetic reasons. This situation applies to both left-hand and right-hand drive cars.
The problem exists that the orientation of the blades on the left-hand and right-hand drive cars requires that the anti-wind lift feature, usually one or more vanes need to face into the airflow and, because of the reverse pattern of wipe, the vanes need to be located on opposite sides of the blade, which side depending on the left or right-hand drive of the car. In the past this has meant the provision of two different blades, one for right-hand drive cars and the other for left-hand drive cars.